Effects of Ozone Depletion

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2 The DiscoveryIn 1985, using satellites, balloons, and surface stations, a team of researchers had discovered a balding patch of ozone in the upper stratosphere, the size of the United States, over Antarctica.British Atlantic Survey Research station, Holly Bay, Antarctic coastTeam who discovered the hole 1985.From left: Joe Farman, Brian Gardiner, and Jonathan Shanklin

5 The ozone layerOzone is a triatomic form of oxygen (O3) found in Earth’s upper and lower atmosphere.The ozone layer, situated in the stratosphere about 15 to 30 km above the earth's surface.Ozone protects living organisms by absorbing harmful ultraviolet radiation (UVB) from the sun.The ozone layer is being destroyed by CFCs and other substances.Ozone depletion progressing globally except in the tropical zone.eng/earth/ozone_layer_depletion/susumu.html

6 Hole Formation Based on Two different mechanisms:Meteorological mechanismMovement of air from one place to another in the upper stratosphereCold temperature in the upper atmosphere causes nitric acid to freeze into crystals forming wispy pink cloudsForms a vortex of tightly twisted winds thus forming a hole in the upper atmosphere

7 Chemical MechanismDifferent chemicals are responsible for the destruction of the ozone layerTopping the list :chlorofluorocarbons (CFC’s)man-made, non-toxic and inert in the troposphereIn the stratosphere are photolysed, releasing reactive chlorine atoms that catalytically destroy ozone

8 A combination of low temperatures and elevated chlorine and bromine concentrations are responsible for the destruction of ozone in the upper stratosphere thus forming a “hole”. (Kerr, 1987)education/education.htm

10 Ozone levels over North America (USEPA, March 1994)No DataNo Dataaqtrnd95/stratoz.htmlComparing the colors of the bands over a particular city, such as Seattle, shows lower ozone levels in 1994 than in 1979Over the U.S., stratospheric ozone levels are about 5 percent below normal in the summer and 10 percent below normal in the winter(U.S.E.P.A. 1994)

11 Stratospheric Ozone and Ultraviolet Radiation (UVR)Ultra-violet radiation (UVR) high energy electromagnetic wave emitted from the sun. It is made up of wavelengths ranging from 100nm to 400nm.UV radiation includes UV-A, the least dangerous form of UV radiation, with a wavelength range between 315nm to 400nm, UV-B with a wavelength range between 280nm to 315nm, and UV-C which is the most dangerous between 100nm to 280nm. UV-C is unable to reach Earth’s surface due to stratospheric ozone’s ability to absorb it. (Last, 2006)

12 Too much ultra-violet light can result in:Skin cancerEye damage such as cataractsImmune system damageReduction in phytoplanktonDamage to the DNA in various life-formsthis has been as observed in Antarctic ice-fish that lack pigments to shield them from the ultra-violet light (they've never needed them before)Possibly other things too that we don't know about at the moment

15 Phytoplankton UV-B penetrates water columns to depths of 30mIncreased UV-B exposureReduces productivity by interfering with processes of photosynthesisDamages DNAAlters nitrogen metabolismInhibits mobilityStudies (1993) conducted in the Weddle SeaEvaluated effects of photosynthesis to UV exposure in the presence of vertical mixing, found:photosynthesis by phytoplankton was strongly inhibited near the surface of the waterrapid mixing, photic zone is extended, severe inhibition of photosynthesis

16 BacterioplanktonPlay critical role in aquatic systemDecomposers - absorb dissolved organic carbon and recycle it back into the environmentPrimary producers – found at the center of food webProne to UV-B stressInhibits growthInterferes with mechanisms for nitrogen fixation and carbon dioxide fixationHigh mortalityEffects dependent on:Where found in the water columnAmount of exposureAmount of protection when moving from one mixing layer to anotherAdaptive Strategy:Pigmentation – absorb more than 90% of UV-B before it penetrates to the genetic materialForm external filaments which protect them from excess UV-B

19 The influence of the UV-B radiation on plant process.Environmental Effects of Ozone Depletion: 1994 Assessment

20 DNA & UV-B Changes shape in DNADNA absorbs UV-B radiationChanges shape in DNAChanges in the DNA molecule mean that enzymes cannot “read” the DNA codeResults in mutated cells or the cells dieCells have developed the ability to repair DNAA special enzyme arrives at the damage siteremoves the damaged section of DNAreplaces it with the proper componentsThis makes DNA somewhat resilient to damage by UV-B

21 Higher Plants However….Experiments were done to determine if increased UV-B is a threat to terrestrial vegetation:FoundHigh UV-B exposure does induce some inhibition of photosynthesisHowever….Studies found no significant effects on photosynthetic productivitySome researchers have concluded that ozone depletion and increase of UV-B not a direct threat to photosynthetic productivity of crops and natural vegetation (Allen, 1998)

22 Difficult to Unmask UV-B EffectsLimitations in controlled and field studies include:Large differences in temperature, precipitation, soil types from year to year and in different locationsUV-B radiation masked by other stresses of land plants such as droughtDrought produces large reductions in photosynthesis and growth masking the effects of UV-BWater stressed plants produce a high concentration of leaf flavonoids (for pigmentation) providing greater UV-B protectionEnvironmental Effects of Ozone Depletion: 1994 Assessment

23 FloweringUV-B radiation can alter both the time of flowering as well as the number of flowers in certain species.Differences in timing of flowering may have important consequences for the availability of pollinators.The reproductive parts of plants, such as pollen and ovules are well shielded from solar UV-B radiation.

24 Can plants protect themselves against increased UV-B?Plant adaptation:Have UV shieldingOnly a small proportion of the UV-B radiation striking leaf penetrates into the inner tissuesWhen exposed to increasing amounts of UV-B, many species of plants can increase the UV-absorbing pigments in their tissuesOther adaptations include:Increased thickness of leaves reducing the proportion of inner tissues exposed to UV-B radiationHave repair mechanisms in plantsincludes repair systems for DNA damage-

26 Global Decline Seen In AmphibiansRange of explanations as to why amphibians are declining, which include:Habitat destructionDiseaseParasitesIntroduction of exotic speciesEnvironmental contaminants and other aspects of global climate change

27 UV-B radiation is still high on the list for the decline in amphibians seen around the worldCauses damage to many species of amphibians at every stage of their life cycle, from egg to adultAffects growth and development in larvaeCausesChanges in behaviorDeformitiesMake amphibians more vulnerable to disease and deathIn adults, causes retinal damage and blindness

30 Over Exposure Suppress immune systemAccelerate aging of skin due high exposureCause an outbreak of rash in fair skinned people due to photo allergy – can be severedermis.multimedica.de/.../ en/13007/image.htm

31 Skin ProtectionProtect the skin against the solar radiation using skin creams with SPFThe greater the numerical value of the SPF the greater the protectionUse lip balm with SPFCover up

32 Over Exposure to UV-B…. Increases the risk of cataractsInduces type of protein that provokes cleaving (splitting) in the lensLeading cause of blindnessThe prevalence of cataract after age 30 is doubling each decadeCauses pterygiumA wedge-shaped growth over the central corneavitreous humorthen the lenscornea is encountered firstlectures/ozone_health

33 Manifestations of… brought on by over exposure to UV-B CancerCataractsbrought on by over exposure to UV-BPterygium

35 What Is Being Done to Counter the Effects of Ozone Depletion?Montreal Protocol (adopted in 1987) – panel of experts was formed to investigate substances responsible for hole formationEstablished policies that prevent future use of certain types of chemicalsStipulated that the production and consumption of compounds contributing towards depletion of ozone in the stratosphere were to be phased out by the year 2000 (2005 for methylchloroform)

36 The Environmental Protection Agency (EPA)Responsible for enforcing the Montreal Protocol within the U.S.The EPA has several programs in place;Regulating and enforcing on-road car and truck air-conditioning systemsRegulating most air-conditioning and refrigeration appliancesTechnician certificationService equipment

37 Signs of Recovery??? There have been some signs of recovery1997 satellite showed a decline of several known ozone-depleting gasesSatellite images show some slowing down of ozone lossHowever….Antarctica - Dec. 2005Recovery is slow../ozone_hole.htm

39 Understanding the futureResearchers would like to see:Stations that measure levels of ozone and surface radiation changes in relation to incidence rate of skin cancer and cataracts - installed in urban areas and in remote regions far from populationsMore studies to determine biological effects (including human) on UVR exposureResearch on protective creams and ointments and their efficiency in preventing skin cancer and malignant melanomaMore surveillance of UV-related damage to other species living in high latitudes for example…..

40 Reports of Sheep in Iceland developing eye disease – no research to support(Last, 1993)

41 Future Evolution of OzoneRemains unclearCurrent models are unable to reproduce ozone variability accuratelyRates of future increases in greenhouse gases are not yet establishedInteractions between ozone depletion and climate change not yet fully understoodContinued monitoring of ozone and ozone-depleting substances is essentialOzone layer recovery expected by 2050Hinges on the complete elimination of atmospheric ozone-depleting substancesReplacements for HCFCs, methyl bromide, and halons are still being sought, and studies of the new compounds must continue(U.N.E..P. Progress Report, 2003)

42 Summing It All Up Meteorological ChemicalThe Ozone is Earth’s only defense against harmful UVRStudies indicate ozone thinning throughout the globe due to 2 mechanisms:MeteorologicalChemicalResearch indicates microorganisms, are extremely sensitive to increasing UV-B levelsThere is a lot of uncertainty and debate among researchers as to the degree in which land plants are affected by UV-BThere is debate in the scientific community in the role UV-B radiation plays on the decline of amphibians seen globallyIn the last decade, there has been an increase in skin cancer and cataracts all related to increase UV-B exposure

43 Efforts Need to Be ContinuedCreate reliable modelsTo gain a better understanding of the effects ozone depletion has on organisms living within different ecosystemsEnforcement of Montreal ProtocolTo reduce concentrations of chemicals responsible for ozone depletionMonitoring chemicals being emittedGain a better overall understanding on just how ozone depletion is affecting our planet...

44 QuestionsWhat are the 2 mechanisms responsible for ozone depletion? Explain each mechanism.Explain 4 effects of ozone depletion.What efforts have been implemented to counter the effects of ozone depletion? Are there any signs that these efforts are working?What are some things scientist would like to see done in order to gain a better understanding on the effects of ozone depletion?